1. Field of the Invention
The present invention relates to a light emitting diode device, and more particularly, to a light emitting diode device with two layers and capable of generating uniform compound lights and having high light emission efficiency.
2. Description of the Prior Art
Light emitting diode (LED) has been outstanding in energy-saving lighting with its features of small size, long device lifetime, high durability, environmental friendliness, and low power consumption. Of all the LEDs, white light LED (or LED with compound lights) combines two or more monochromatic lights and has been widely used in indicating lamps and display devices in information technology, communications, and consumer electronics products. In addition to improving the light emission efficiency, the unevenness of lights from the LED also requires an urgent solution in the study of compound LED.
Please refer to FIG. 1, which is an illustration of a light emitting diode packing with a phosphor layer disclosed in the U.S. Pat. No. 6,417,019. To improve the evenness of a compound light LED, a special process is adopted to deposit an extremely thin phosphor layer 2 onto the surface of a LED chip 1 in order that the lights emitted from the chip 1 can interact immediately with the phosphor powder inside the phosphor layer 2 after travelling a negligible distance. The lights are therefore transformed into compound lights and emitted from a light package (including a reflective cup 3).
Such package structure, however, brings about some following disadvantages:
The extremely thin thickness of the phosphor layer 2 on the chip 1 greatly complicates the procedure and increases manufacture cost.
Direct covering of the phosphor layer 2 on the chip 1 puts some lights emitted from the chip 1 to reflect backward and be absorbed by the chip 1 after running into the phosphor powder.
Such process can only be utilized for flip-chip type LED.
The chip 1 emits the lights as a point light source. Although, the reflective cup 3 increases the light emission efficiency, it still narrows the light angle of the chip 1.
After improving the evenness of lights, the prior art can not further increase, or even maintain the light emission efficiency of the LED at the same time.